From: ecamin (ecamin_at_earthlink.net)
Date: Wed Aug 28 2002 - 21:45:51 EDT
Thanks Steve. Having retired from Product Safety 12 years ago, I had
forgotten that. However it was usually connected to the ground side of a
polarized plug. I'm not sure why they felt it necessary to have added the
3rd gnd prong on wall transformers. Changes like that usually quietly occur
from over reaction to a field incident. Even if an outlet was miswired a
meg resistance would safely discharge a 20kv static charge to the hot side
of the line. My TP600 has the third prong. I'm guessing that it must have
something to due with the transformed being in the power cord instead of
wall attached.
Ed
----- Original Message -----
From: "Steve C." <stevec50_at_yahoo.com>
To: <thinkpad_at_cs.utk.edu>
Sent: Wednesday, August 28, 2002 4:39 PM
Subject: Re: [TP 600 series] Power supply questions
> Actually it does protect the thinkpad. The ground is
> connected to the thinkpad frame through a 1M resistor
> to protect it from static discharges, such as sparks
> from walking across a carpet, static from clothing,
> lightning, etc.
> and drains the charge off to ground when you touch it
> if you are statically charged or if there is a
> lightning strike on the phone line or whatever.
> --- ecamin <ecamin_at_earthlink.net> wrote:
> > The third prong has nothing to do with the operation
> > of the Thinkpad. It's
> > there to protect you from shocks. Having said that,
> > a cheater adapter is
> > available from every hardware store that eliminates
> > the third prong. They
> > usually have a screw connection so that it can be
> > grounded under the screw
> > that holds the outlet plate on. That of course
> > assumes that there is a
> > ground on the electrical box. As long as you aren't
> > standing on a concrete
> > floor or are touching a metal ground object, you
> > won't be shocked. Use at
> > your own risk and wear rubber sneakers or rubber
> > bottom shoes. Leather
> > sometimes may conduct. Without the ground the only
> > hazard is that the
> > transformer my shortout and pass 120v to the TP.
> > Your worse hazard is the
> > phoneline connected to the TP.
>
>
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